1. Field of Invention
This invention relates to technique for recovering hydrocarbon fluids in a process flow; and more particularly to recovering bitumen from a coarse tailings line.
2. Description of Related Art
In a coarse tailings line that goes from a separation vessel (such as a gravity separation vessel or a PSV) to a tailings pond in an oilsands separation plant, trace amounts of bitumen of up to 1% or more may be present in the waste (tailings) line that goes to a tailings pond.
The coarse tailings line is a slurry transport process, which means that water is used to transport the waste to the tailings pond. The waste will include the various sands, clays, water and other natural materials that were separated from the bitumen in the separation plant. In the tailings pond, the solids and sediment settle out, leaving behind the process and naturally occurring water. Any leftover bitumen in the coarse tailings will be discharged to the tailings pond, presenting a potential environmental hazard, as well as a loss of valuable hydrocarbon content.
The pumping of the tailings in the coarse tailings line will cause additional conditioning of the tailings mixture leading to the potential separation of any bitumen in the tailings from the sand and clays in the tailings. This separated bitumen will tend to “float” along the top of the tailings pipe.
One known method to capture the bitumen in the tailings line is to use a skimmer at the very end of the tailings line prior to the tailings pond to skim off the bitumen in the pipe with the use of a diverter plate. The skimmer plate skims off the bitumen and directs it to a tank, with the remaining tailings going to the tailings pond.
The issue with this method is that there is no way to know how much bitumen is present in the coarse tailings line. With a fixed diverter plate, in some instances, too much water will be captured when little bitumen is present, and in other cases, too little bitumen will be captured, with significant amounts of bitumen being directed to the tailings pond.
In view of this, there is a need in the industry to provide a way to know or determine how much bitumen is present in the coarse tailings line. Moreover, there is also a need in the industry to provide a way to capture more bitumen and less water from the process flow, as well as to reduce the amount of bitumen being directed to the tailings pond.